The present invention relates to filters for separating hydrocarbons and contaminants from liquid streams.
The containment, collection and prevention of the discharge of diesel oil present as unburned fuel in diesel engine exhaust, and the reduction of particulate and other contaminants in emissions from diesel engines, is an on-going issue. In marine applications, stringent laws (e.g., 33 USC 2702 “The Oil Pollution Act”) have been enacted to protect the environment, which have necessitated the significant control of emissions to avoid costly fines. Similar emphasis has been placed on reducing emissions from heavy duty trucks and public transportation busses.
One known technique for removing hydrocarbons from an exhaust stream is to direct the dry exhaust stream through a filter. The filter typically includes one or more filter elements in a cartridge form, for example with high-temperature ceramic fiber wound in a diamond form around a perforated support tube. The flow is outside-in, with the support tube fluidly connected at its downstream end to the outlet in the filter housing, and then to atmosphere. The elements can be connected in parallel, or in series. The ceramic fiber used in this application is typically a significant expense.
Fiber mats comprising aromatic polyamides are also known for removing hydrocarbons from the dry exhaust gas stream (see, for example, U.S. Pat. No. 3,871,850). It is believed such mats provide good filtration, but hydrocarbons are particularly difficult to remove from a gas stream and can quickly clog such a mat. A clogged element can cause unacceptable pressure drop across the filter, and require frequent replacement. As can be appreciated, the frequent replacement of cartridges increases maintenance expenses and can interrupt the continued use of the boat.
Another known technique for reducing emissions from diesel engines is to first “scrub” the emissions. In this technique, the gas stream is impacted on water in a closed chamber. The stream is cooled and the velocity of the stream is reduced. Some of the oil collects directly on the surface of the water, while the remainder of the oil is absorbed (emulsified) in the water, and then floats to the surface. Aromatic hydrocarbons and related fumes and particulate are also absorbed and contained during the water/gas contact cycle. The oil and particulate in the water are then collected such as by a pickup tube, and processed by an oily water separator or filtration system. One such scrubber is manufactured by EcoSound of Tarpon Springs, Fla., under the mark/designation EPS 5000 Exhaust Processing System.
While a scrubber has certain advantages over a dry gas filtration system. The filter elements useful for processing the collected hydrocarbons in such scrubber systems have also generally been expensive and/or have lasted for only a short period of time before requiring replacement. Thus, the drawbacks have remained primarily the same as with dry exhaust filters.
Thus, it is believed there is a demand in the industry for a filter which removes emissions and other contaminants from diesel exhaust gasses, particularly in marine applications, which has a reduced cost, is simple to manufacture, install and maintain, and has an improved operating life before replacement is necessary. It is believed the demand is great for such a filter particularly in scrubber systems to remove hydrocarbons and other contaminants from a liquid stream passing through the scrubber.